Williams plays Addison's mother Bizzy and first appeared in an episode last year.

Speaking to TV Guide, Rhimes explained that Bizzy will have reservations about Addison's relationship with Sam.

"Bizzy likes Sam a great deal, but I don't necessarily know that Bizzy likes Sam when he's with Addison," she said. "Bizzy's return is going to have a very big effect on Addison and it will leave her with a lot of interesting things to deal with."